Gas-filled electric incandescent lamp



Oct. 23, 1928.

J. BERGMANS El'AL GAS FILLED ELECTRIC rncmmzscam' mu? Filed Nov. 4, 1927Inventor's Jan B ergmans Theodorus J. AMand Their Attorney.

Patented Oct. 23, 1928.

UNITED STATES PATENT OFFICE.

JAII BERGMANS AND 'I'HEODORUS JOSEI'HUS JACOIBUS ALPHONSUS MANDERS, OFEIND- HOVEN, NETHERLANDS, ASSIGNOR T0 GENERAL ELECTRIC COMPANY, A CORPO-BATION 01? NEW YORK.

GAS-FILLED ELECTRIC INCANDESCEN'I LAMP.

Application filed November 4, 1927, Serial No. 231,130, and in theNetherlands December 21, 1928.

The invention relates to an electric incandescent gas filled lamp, suchas a projection lamp with a highly concentrated filament and a fillingof gas inert to the filament. The filament in such lamps, which have anextremely high light intensity, is heated to very high temperature, withthe result that evaporation occurs during which particles emitted fromthe filament deposit on the inside of the surrounding bulb. Owing tothis precipitation of these particles, the inside of the bulb becomesblackened or covered by a soot-like layer, which decreases thebrightness of the lamp and causes the lamp to become unsuitable forpurposes of illumination. Naturally, this blackening greatly diminishesthe efficiency of the lamp and methods have been sought to prevent ordiminish it.

One method which has been suggested is to divide the lamp into sectionsin such a way that the differences in temperature in the differentsections cause inside the lamp a flow of gases suifieient to conduct theparticles thrown ofi' by the filament into the comparatively large bulbaround the filament to some other part of the bulb where they do nothave a detrimental influence on the radiation of light. However, thismethod requires that separate artitions be constructed inside the lamitse f in order to divide it into sections.

T e purpose of the present invention is to secure a forced draft insidethe lamp without the use of partitions and without requiring that thelamp be divided into separate sections. To this end the part of the bulbthrough which the light rays originating from the filament pass has beendesigned in such a way that it is tubular, surrounds the filamentclosely and is of comparatively small bore. The concentrated filament islocated at the end of the tubular part of the bulb, through which theleads for supplying current to the filament extend. In use the bulb ispositioned in such a way that the filament is located in the lower partof the bulb.

The gases, heated directly by the filament, will rise and will beconducted by means of the hot leads which carry the current to thefilament to a part of the bulb where these gases may cool off. Afterthis cooling has occurred the comparatively cool gases move downwards,following the inside of the tubular part of the bulb, and thus return tothe filament. The cool gases moving downward act as though they surroundthe upward current of hot gases, and when reaching the lower part of thebulb the cool gases will move with some force along the inside of thislpart which surrounds the filament closely, as

as been mentioned above. Due to the small bore of the tubular part ofthe bulb immediately surrounding the filament no eddies or vortexmotions occur in the currents of gases and, in addition, the desirableresult is secured that the currents of gas are extremely swift at thisspot so that any black material which tends to deposit there will bescoured off and carried along by the current of gases to another spotwhere the current is less swift.

In order to secure a good cooling effect at a selected place the tubularpart of the bulb may be expanded reatly to form a bulbous or sphericalchamdier in the neighborhood of the stem, while the filament is mountedin the end of the tubular part remote from this chamber and as far aspossible from the stem.

Two functions result from the expanding of the tubular bulb into achamber, viz in the first place a cooling chamber is formed, and in thesecond place a space is secured in which the fast moving gases losetheir speed and permit preci itatlon of the particles thrown ofi by thefi ament. In order to increase the cooling artificial cooling may beapplied to the bulb in the neighborhood of the stem.

The construction also has the advantage that the filament is surroundedby a tubular glass envelope occupying very little space, while theexpanded part of the bulb is located at considerable distance from thefilament. Owing to this feature the lamps are very suitable for use forprojection purposes. This construction has certain advantages in opticalsystems using a lens or condenser, as well as in those using a mirror.In the first place, the lens or condenser can be placed much closer tothe light source, allowing a more compact construction, and in thesecond place the expanded part of the bulb is outside the cone of light,so that the light rays are less deformed or weakened. It is, of course,understood that the bulb must be manufactured of a kind of glass whichcan withstand the high temperatures which are present in the immediateproximity of the filament.

In the accompanying drawing which shows one embodiment of the invention,a concentrated filament 1 is mounted on the ends of a pair of strai htparallel leads 2 and 3 which support the filament and also supplycurrent to it through the leading in wires 5 and 6 in the stem and thebase 7 which is connected by a socket to a source of current. Thefilament and the leads are enclosed in a sealed gas filled bulb whichcontains an inert as and has a bulbous tubular part 8 of smalldioreclosely surrounding the filament 1, and. which is expanded into aspherical part or cooling chamber 9 in the neighborhood of the base 7.

When the lamp is lighted the filament 1 located near the sealed end ofthe tubular part 8 of the bulb will glow and consequently thesurrounding inert gas will be heated. A similar heating of the gas takesplace between the leads 2 and 3 which are preferably proportioned to bebrought by the normal current flowing through them to a temperature highenough to heat the adjoining and surrounding gas sufiiciently to causeit to ow upwards along the leads. If the lamp is mounted base up so thatthe base 7 is above the filament 1, either in a slanting or in avertical direction, then the heated gas will flow upwards along theleads with a velocity great enough to carry alon the particles offilament material and W51 flow into the spherical part or coolingchamber 9 which has a bore so much greater than that of the tubular part8 that it loses velocity and deposits the particles of filamentmaterial. The heated gas is cooled off at the surface of the sphericalchamber, whereupon it flows downwards along the sides of the tubularpart 8 until it reaches the lower end of the tubular part 8 of the bulb,where it will be again reheated by the filament. As the tubular part ofthe bulb which immediately surrounds the filament is of small bore, noeddies or vortex motions occur in the currents of gas, which attain acomparatively high velocity, thus preventing the deposition on the bulbwalls at this place of articles emitted by the filament. By means 0 thisinvention the glass of the lampris kept clear for the entire life of thelamp exactly at those places through which the light rays have to pass.

What we claim as new and desire to secure by Letters Patent ofthe/United States, is:

1. A gas filled incandescent electric lamp comprising a pair of parallelleads propor- "tioned to be heated by the normal current flowing throughthem to a temperature sufiicient to cause a flow of the adjoining gaswhen the lamp is lighted, a concentrated filament on the end of saidleads, and a sealed tubular bulb containing inert gas and enclosing saidleads and said filament with one end ad acent said filament and of abore such that when the lam is lighted currents of gas free from eddiesow along said leads and along said bulb walls with a velocity so greatthat blackening of the bulb walls in the vicinity of the filament issubstantially absent.

2. An incandescent electric lamp comprising a sealed bulb having astraight tubular portion closed at one end and expanded near the otherend into a bulbous chamber of considerably greater diameter than saidtubular portion, a pair of straight parallel leads mounted in saidtubular portion and extending from near its closed end into saidchamher, and a concentrated filament mounted on the ends of said leadsnear the closed end of said tubular portion of the bulb, said tubularportion having a bore small enough to cause the currents set up in thegas in the bulb when the lamp is lighted to flow with suflicientvelocity to maintain the bulb walls adjacent said filament substantiallyfree from blackenll'l A gas filled incandescent electric lamp comprisinga sealed bulb containing an inert gas and having a straight tubularortion and a portion at one end enlarged to orm a cooling chamber, astem extending into said cooling chamber, a base on said coolin chamberadjoining said stem, a pair of straight leads secured to said stem toextend through said cooling chamber and into said tubular portion andproportioned to be heated by the normal current flowing through them toa temperature sufiicient to cause the gas to flow along them, and aconcentrated filament connected to said leads adjacent the other end ofsaid bulb with a clearance between aid filament and the walls of saidtubula portion so slight as to cause high velocity currents of gas freefrom eddies to flow along the walls of said tubular portion while thelamp is lighted.

4. An incandescent lam com rising a stem, a pair of straight para lellea s extending from said stem, a concentrated filament on the free endsof said leads, and a sealed bulb containing inert gas and enclosing saidleads and filament, said bulb having a bulbous chamber adjacent saidstem and surrounding said leads near said stem and a straight tubu larportion extending from said chamber to enclose said leads and saidfilament with the opening into said chamber obstructed onl by saidleads, said tubular portion having a bore small enough to cause currentsin the gas free from eddies and of sufiicient velocity to preventblackening of its walls near the filament, and said chamber having abore sufficiently greater to permit the currents to decrease in velocitysufliciently to deposit in said chamber particles of filament materialcarried by the currents.

' 5. An incandescent electric lamp comprising a sealed bulb having astraight tubular leads near th 1 d d portlonpf small bore closed at oneend and tion of the blil en of Sald tubular pm a spherical chamber ofconslderable grester In witness whereof, we have hereunto set 10diameter at the other end, a, pair of straight our hands this 8th day ofOctober 1927.

5 leads extending through the opening of said JAN BERGMANS.

tubular portion lnto said tubular portion, THEODORUS JOSEPHUS JACOBUSand a concentrated filamentmounted on said ALPHONSUS MANDERS.

CERTIFICATE or CORRECTION.

Patent'No. 1,688,777. in Granted October 23, 1928, to

JAN BERGMANS ET AL.

It is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction as follows: Page 2,line 15, strike out the word "bulbous" and insert the same before theword "spherical" in line 17; and that the said Letters Patent should beread with this correction therein that the same may conform to therecord of the case in the Patent Oftice.

Signed and sealed this 27th day of November. A. D. 1928.

M. J. Moore, (Seal) Acting Commissioner of Patents.

ing a sealed bulb having a straight tubular leads near th 1 d dportlonpf small bore closed at one end and tion of the blil en of Saldtubular pm a spherical chamber of conslderable grester In witnesswhereof, we have hereunto set 10 diameter at the other end, a, pair ofstraight our hands this 8th day of October 1927.

5 leads extending through the opening of said JAN BERGMANS.

tubular portion lnto said tubular portion, THEODORUS JOSEPHUS JACOBUSand a concentrated filamentmounted on said ALPHONSUS MANDERS.

CERTIFICATE or CORRECTION.

Patent'No. 1,688,777. in Granted October 23, 1928, to

JAN BERGMANS ET AL.

It is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction as follows: Page 2,line 15, strike out the word "bulbous" and insert the same before theword "spherical" in line 17; and that the said Letters Patent should beread with this correction therein that the same may conform to therecord of the case in the Patent Oftice.

Signed and sealed this 27th day of November. A. D. 1928.

M. J. Moore, (Seal) Acting Commissioner of Patents.

